For the energy consumption of a whole building, the energy consumption of an air conditioning system takes a great proportion, which is about 40˜50% generally. In addition, for the energy consumption of the air conditioning system, chiller plant room (which comprises chillers, chilled water pumps, condenser water pumps and cooling towers) will take about 60%˜70%. Regarding to an office building using an electric cooling, the power consumption for all year of an air conditioning cooling source (chiller plant room), i.e. chillers, chilled and condenser water pumps and cooling towers, will take about 30˜35% of the power consumption of the whole building for all year.
The cooling operational process of an air conditioning system comprises the following. The chillers produce chilled water with predetermined temperature. Chilled water is transported to air terminals through chilled water pumps, to conduct a thermal exchange with indoor air, absorb the heat indoor and remove the redundant moisture in the indoor air, to meet the requirements of the indoor environment. The temperature of the chilled water rises after absorbing the heat indoor, and then the chilled water is cooled again by chillers for recirculation. The heat generated by chillers during the operation, which is mainly the heat absorbed from the indoor air by chilled water, and also including the heat generated from the inherent energy loss due to some factors such as friction during the operation of the chillers, is absorbed by the cycled condenser water. The condenser water is transported to cooling towers through the condenser water pumps so as to perform the heat and humidity exchange with outdoor air by dissipating heat and moisture into the atmosphere finally.
Therefore, it is very important how to maximally save the energy consumption of a chiller plant room for reducing the energy consumption of the whole building. In the prior arts, chillers may operate with lower chilled water supply temperature and lower chilled water flow rate, which may lead to higher energy consumption of the chillers and lower energy consumption of the chilled water pumps. Alternatively, lower return chilled water temperature and higher chilled water flow rate are adopted. Likewise, to the same cooling output, chillers can be operated under a lower condensing pressure, which leads to lower energy consumption of the chillers; however, a higher condenser water flow rate is required for the lower condensing pressure, leading to a higher energy consumption of the condenser water pump. Or otherwise, adopt an operation mode of higher energy consumption of the chillers and lower energy consumption of the condenser water pumps. Therefore, an optimized energy-saving method is needed.
In the prior arts, some methods may be feasible in a stable laboratory condition, however, in the actual operational process, all the apparatuses in the chiller plant room are in the continuously operating state, and the cooling loads and the weather parameters will vary at any moment, which may cause the actual parameter values collected not having regularity, so the energy consumption model can not be optimized and even a contrary effect might be caused through adjusting the energy consumption model with the above methods.
Therefore, in the actual operation, it is impractical to find out the best operation condition point of highest efficiency of the whole chiller plant room with the above methods. In addition, none have the prior arts established the heat exchange model of the cooling tower, which will certainly reduce the effect of its energy consumption control.